So-called Swiss turning tool assemblies and their components, are special purpose tools designed for use in swiss-style CNC machines (lathes) which are typically used for high precision machining applications. An example Swiss turning tool assembly of the field to which the present application is directed (Swiss turning assemblies for turning applications) is further detailed in U.S. Pat. No. 9,901,986, assigned to the present applicant and incorporated herein by reference for understanding the unique requirements of Swiss tool assemblies.
Swiss tool assemblies achieve high precision is achieved by the workpiece being held close to a bushing to minimize overhang and maximize stability and structural strength. Hereinafter the names “Swiss” or “Swiss turning” are sometimes omitted for conciseness only, but it should be understood that the subject matter of this application is specifically directed to only to turning inserts, tool holders and assemblies designed for specific Swiss-style machining.
The design of Swiss inserts is limited by the requirement to machine very close to the bushing and other tool assemblies in a gang 100 (see, e.g., FIGS. 1A and 1B of the present application, the drawings of which, but not the numbers, correspond to figures in U.S. Pat. No. 9,901,986).
As shown in FIGS. 1A and 1B, there are four tool assemblies 102 shown. Each tool assembly 102 comprises a tool holder 104 and a turning insert 106. It is noted that turning inserts 106 are subjected to higher lateral forces than parting-off or grooving inserts, due to their also being used in turning operations (i.e. lateral machining in the direction designated DL). It is however noted, that turning inserts may also be configured with a grooving capability. As noted above, the name “turning” may be omitted for conciseness only, when referring to inserts hereinafter.
The turning inserts 106 have a rake surface 108, above which chips flow (not shown), and flank surfaces 110A, 110B. A screw hole 112 and 114 extend through the flank surfaces 110 to clamp each insert 106 to a respective tool holder 104. A cutting edge 116 is formed at an intersection of at least the externally located the flank surface 110A and the rake surface 108.
Due to the inserts 106 being in close proximity to each other in the gang 100, and directly above one another due to the nature of Swiss-style CNC machining, the inserts do not have a clamping hole, such as a screw hole, extending through the rake surfaces 108 thereof but rather the screw holes 112 extend through the flank surfaces 110 thereof for accessibility purposes. It will be understood that such clamping arrangement (screw hole 112 extending through the insert's flank surfaces 110) avoids the difficulty caused by the closely packed tool assemblies and is a popular manner to secure a Swiss cutting insert.
Nonetheless, it will be noted that the cutting portion 118, to use an improvised name for the front portion of the insert shown by the arrow designated 118, is unsupported by the tool holder 104.
In the further prior art example shown in FIGS. 2A and 2B, a prior art Swiss tool assembly 200 of the Applicant is shown.
Tool assembly 200 comprises a tool holder 204 and a turning insert 206. The turning insert 206 has a rake surface 208, above which chips flow (not shown), and flank surfaces 210.
Contrary to the previous example, the clamping arrangement includes a clamping hole 212 extending through the rake surface 208, and clamping is achieved through rotation of a screw 214, accessible through a flank surface 216 of the tool holder 204, and not the insert's flank surfaces 210. The screw 214 causes a lever 218 that extends through the clamping hole 212 to move in a backwards and downwards direction D1 to clamp the insert 206 to the tool holder 204.
In contradistinction to the previous example, the insert 206 of tool assembly 200 is more supported by the tool holder 204 than the previously described insert 106, nonetheless the clamping arrangement thereof is considerably more complex and expensive.
It is an object of the present application to provide an improved swiss turning insert, tool holder and tool assembly, particularly with high structural stability yet a simpler and more user friendly clamping arrangement.